I recently installed an ASUS Xonar DG 5.1 sound card and now I have a few questions. But first, here are my current Audio Center settings, which I configured based on someone else's recommendations on some other forum.

For every "audio channel" option (2, 4, 6, 8):
Sample Rate is PCM 44.1 KHz
Analog Out is Headphone
Dolby Headphone is checked (with DH-2 setup)
7.1 Virtual Speaker Shifter is checked

I use 2 channels for music and 8 channels for games. Sounds great, but I don't really know what I'm doing. Is it pointless to have 7.1 Virtual Speaker Shifter checked if I'm using less than 8 channels?

And the big question: how can I determine whether a game supports 8 audio channels? Does Quake Live? Quake 1? Reflex? Etc.